Known beverage preparation machines contain apparatus for frothing and/or heating milk. In this case, milk is, for example, sucked into a vacuum chamber formed in the respective apparatus for frothing and/or heating milk, in which a vacuum is achieved by introducing (water vapour) steam (e.g. in the form of a steam jet) according to the Venturi principle, through a milk suction hose from a usually separate milk container and is heated therein by the steam and possibly frothed with added air in order to produce heated milk or milk froth or a mixture of heated milk and milk froth. Beverage preparation machines having an integrated apparatus for frothing and/or heating milk are also known which make it possible to produce as desired coffee (without added milk) or heated milk (without added coffee) or white coffee (without added milk froth) or specialty coffees which contain milk froth or frothy milk (for example, cappuccino or latte macchiato).
A problem with all these apparatus which handle milk is that milk residues remain in the system for a fairly long time. Milk perishes rapidly, particularly promoted by lack of cooling. In order that the milk located in the system after a milk withdrawal does not perish or become contaminated, the parts coming in contact with milk should be thoroughly cleaned or flushed at the shortest possible time intervals.
For this purpose, the apparatus for frothing and/or heating milk can be cleaned by passing, for example, steam therethrough without introducing milk.
A separate cleaning of the milk suction hose in which milk residues are also located can be carried out by removing this and flushing it by hand under running water.
Another method for cleaning the milk suction hose is known in which one end of the milk suction hose through which the milk is otherwise sucked into the milk container is removed from this, dipped temporarily into a container containing cleaning liquid and then a milk withdrawal is made at the beverage preparation machine, wherein the cleaning fluid (instead of milk) is then sucked through the milk suction hose and this is thereby cleaned or flushed. However, these steps are cumbersome and in addition the user is forced to touch the outer circumference of the milk suction hose which had been previously dipped in the milk, whereby the user gets his hands dirty. Also that outer circumference of the milk suction hose can become contaminated by the user. The milk suction hose could then be contaminated with bacteria in conjunction with the milk as growth medium. After flushing the milk suction hose with the cleaning fluid, it is expedient to flush the milk suction hose with a suitable fluid, for example, water in order to ensure that residues of the cleaning fluid possibly present in the milk suction hose are eliminated and the milk suction hose is therefore ensured to be free from residues of the cleaning fluid. After this process water residues can still be present in the hose. These water residues are sucked into the apparatus for frothing and/or heating milk during a next withdrawal of milk and could result in a taste impairment particularly if the water has been left standing after a fairly long non-usage of the beverage preparation machine.
At present, the milk suction hose is either not flushed at all, flushed by hand, as described above or it must be connected to a separate water outlet of the beverage preparation machine.
EP 1 797 801 discloses an apparatus for supplying milk in which one end of a milk suction hose is connected to an apparatus for frothing and/or heating milk and the other end is dipped in a milk supply in a milk container. In order to clean the milk suction hose, it is proposed in this case to remove this end of the milk suction hose located in the milk supply in the milk container and to connect this to a cleaning apparatus which dispenses hot water and/or steam. Hot water and/or steam is then withdrawn from the cleaning apparatus, passed through the milk suction hose and the apparatus for frothing and/or heating milk, thereby flushing this apparatus and the milk suction hose and is finally removed through the milk outlet.
It is disadvantageous in this connection that for this purpose the user must touch outer regions of the milk suction hose which are wetted with milk so that the user gets his hands dirty. In addition, these regions can possibly be contaminated by the user with bacteria in conjunction with the milk as growth medium, which can promote the multiplication of harmful bacteria. Since this region of the milk suction hose is subsequently again dipped into the milk of the milk container, the bacteria can then be transferred into the milk which can lead to a health hazard. It is also disadvantageous that only hot water and/or steam is passed through the milk suction hose which can lead to inadequate cleaning depending on the degree of contamination. In addition, water residues are still present in the system after this process.
EP 2 020 197 discloses a beverage preparation machine having a cleaning apparatus for cleaning internal lines which carry milk. In this case, various valves must be controlled or actuated for flushing. A valve 14 can be switched so that a cleaning fluid can flow from a source 13 into the milk path. Various valves are switched so that in each case a closed circuit is formed through which the cleaning fluid can be pumped by means of a pump 11. Various circuits or paths can be switched for the cleaning fluid in order to cover various regions of the milk path.
An automatic cleaning of the milk outlet 2 is not provided. This must be cleaned separately. Special measures are required to clean a part of the milk path in the vicinity of the milk outlet. To this end the milk outlet must be removed and replaced by a cartridge 22, thereby creating a closed circuit which includes the said part of the milk path in the vicinity of the milk outlet. At the end of the cleaning procedure the cleaning fluid can be discharged via a separate outlet 19—controlled via valves 18 and 31.
In this connection it is disadvantageous that a large number of additional devices are required for cleaning the milk path which leads to high costs and results in more expensive maintenance. Automatic cleaning of the milk outlet is not possible or requires the dismantling of the milk outlet and a separate cleaning. In addition, a complex and expensive cartridge must be coupled to this position after dismantling the milk outlet which is very expensive and in particular time-consuming.